1. Field of the Invention
This invention relates to a wiper apparatus used for wiping a wiped surface, for example, a windshield of a motor vehicle and, more particularly to a wiper control for actuating a wiper blade reciprocatingly by changing a rotational direction of a wiper motor.
2. Description of the Prior Art
Heretofore, there has been used a wiper apparatus having structure that rotational motion of a wiper motot in one-way direction is converted into reciprocating motion of a wiper blade through a wiper linkage.
And, a wiper apparatus is disclosed in Japanese Patent Publication No. 60-4678/85 (Kokoku), which has structure that a wiper blade is droven reciprocatinly by changing a rotational direction of a wiper motor when the wiper blade arrives at the predetermined turning position without using the wiper linkage.
In a wiper apparatus is disclosed in Japanese Patent Disclosure No. 62-96154/87 (Kokai), which has structure that a wiper motor may be released from its restricted state by shifting a lower turning position of a wiper blade and changing a wiping area of the wiper blade in order to solve a problem in that the wiper motor is sometimes damaged owing to overheating caused by an overcurrent flowing in the wiper motor when the wiper blade is restricted to move by snow lying in a lower turning position (on the side of the stop position) of the wiper blade in case of snowfall.
However, in the conventional wiper apparatus disclosed in the Japanese Patent Disclosure No. 62-96153/87, there is a limit in changeable range of the wiping area of the wiper blade, therefore, there is not consideration about a case the wiper blade is obstructed to move in the position beyond the changeable range of the wiping area by snowfall in large quantity, for example.
And, the improvement disclosed in the aforementioned Japanese Patent Disclosure No. 62-96153/87 is devised for a wiper apparatus having the structure that the rotational motion of the wiper motor in one-way direction is converted into the reciprocating motion of the wiper blade through the wiper linkage. In a wiper apparatus of a type of changing the rotational direction of a wiper motor and having a wiping angle of 180 degrees or so, there is a problem since there is the possibility that the wiper blade is obstructed to move by snow laying in the turning position on the opposite side of the stop position of the wiper arm.